Democrat Edward J. Markey, a 37-year veteran of the US House, cruised to victory Tuesday over Republican newcomer Gabriel E. Gomez in the US Senate special election, despite running a low-key campaign that drew record low voter turnout.

Backed by an army of Democratic activists, unions, and advocacy groups, Markey rolled up large enough margins in the party’s strongholds around the state to overwhelm Gomez, who failed to generate the strong enthusiasm he needed among moderate independents and within his own Republican base.

The final results showed Markey beating Gomez about 55 percent to 45 percent.

Markey, 66, now heads to the Senate to finish the final 17 months of John F. Kerry’s term and protect the Democrats’ grip on the chamber, where the party holds a 54 to 46 majority.

Voter turnout was 27 percent statewide, below even the dismal projections of state elections officials. About 1.16 million voters cast ballots Tuesday, compared with the 2.3 million who voted in 2010, when turnout was 54 percent.

“I am a son of Malden, but I do not go to occupy a seat in the Senate,” Markey told the crowd at the Boston Park Plaza Hotel after his win. “I go there to stand for you, to speak for you, to seek change that lifts up your families and your future.”

Gomez told his supporters at the Seaport Hotel that he had not memorized his concession speech because he had not planned on delivering it. “I apologize for coming up short on this mission,” the former Navy SEAL said. “You are the ones who deserve better. You stood by me, you ran with me, and you motivated me every step of the way.”

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Markey’s victory, while solid, fell short of the crushing blow that Democrats hoped he would deal to Gomez and that would help him avoid drawing a GOP opponent in next year’s general election, when he must run for a full, six-year term.

Republicans will also be able to point to the race as evidence that Democrats, unable to pull off a wider victory in a party stronghold like Massachusetts, are in a weak position in next year’s congressional races to defend their majority in the US Senate.

Gomez can now present himself as a credible future candidate for statewide office. With his business background, moderate social views, and Latino heritage, he could still argue that he is a fresh face for a party that wants to broaden its appeal. Despite the loss, the National Republican Senatorial Committee openly encouraged Gomez Tuesday night to run against Markey again in 2014.

The lackluster race, which began when Kerry vacated his Senate seat to become secretary of state in early February, was an anomaly for Massachusetts, which has a rich history of spirited Senate campaigns with big, clashing personalities and sharp arguments about issues.

When Gomez, a little-known private equity investor, scored a surprising victory in the three-way GOP primary in April, many in the political world saw the makings of another full-throttled Senate battle like the Scott Brown-Martha Coakley contest of 2010.

As with that campaign, this one pitted a fresh face with a compelling personal story and a military background against a cautious Democratic insider. But a major showdown never materialized.

Markey focused on lowering the profile of the race, hoping to cobble together a coalition of liberal activists who pay attention to politics even when the broader electorate tunes it out. That insider strategy was designed to deny Gomez a chance to catch fire. Often, Markey would hold only a handful of public events each week.

Gomez, for his part, struggled to articulate his positions on several issues, including abortion and insurance coverage for contraception. In addition, he never benefited from the kind of deep voter discontent that propelled Brown into the Senate.

That year, the Tea Party movement was ascendant, the country was facing economic woes, and many were angry over President Obama’s health care bill. This year, voters seemed uninterested in the third Senate race in just over three years. Many said they were tired of politics and more consumed with news about the Boston Marathon bombings and the Boston Bruins. Temperatures in the 90s on election day added another hurdle for people getting to the polls.

Markey, first elected to the House in 1976, came into the contest as the establishment favorite, endorsed by Kerry, Victoria Reggie Kennedy, and the Democratic Senatorial Campaign Committee. In the primary, he was never seriously challenged, easily defeating his colleague, US Representative Stephen F. Lynch.

In the general election, he ran on two main issues, his support for legalized abortion and an assault weapons ban, even though polls have shown that voters are most concerned about jobs and the economy. He used the issues of gun control and abortion to define and damage Gomez, linking him to the more conservative elements of the Republican Party in a fusillade of negative
ads.

Markey also tapped heavily into the party’s national and local fund-raising networks to raise and spend more money than Gomez, who did not draw strong support from national GOP donors.

Gomez tried to paint Markey as an out-of-touch creature of Washington and a lock step partisan who would only deepen the dysfunction in Congress. He made term limits a centerpiece of his campaign and promised to reach across party lines to overhaul the immigration and tax systems. But his promise to bring a fresh perspective to Congress never gained traction, perhaps because Massachusetts has a tradition of long-serving senators like Edward M. Kennedy, who held his Senate seat for 47 years, and Kerry, who was in the Senate for 28 years.

Gomez also faced a formidable Democratic political operation. Party leaders had vowed never to be beaten again after the humiliating defeat in January 2010 when Brown shocked the political world by winning Kennedy’s seat. The same field operation that avenged that loss by electing Elizabeth Warren over Brown last year was a key in Markey’s victory. The state Republicans have never been able to match the Democrats’ organizational muscle.

Markey’s victory sets off a scramble to fill the remainder of his House term for the district that runs from Revere to Framingham and Hopkinton. A host of up-and-coming Democrats – including three state senators, a state representative, a Cambridge city councilor, and the Middlesex sheriff — have begun assembling campaigns. That election is expected to be scheduled for the fall.